It's a full chain of events that one thing lead to another. People invest money into companies in order to make more money, but they don't make more money just because the company had profit - it that was the case nobody would have sold it to them. For the investors to profit from owning part of a company, it needs to increase the amount of money it makes compared to when the investor jumped in. With the companies being negotiated at all times, it needs to increase its revenue at all times as well. So companies' objectives are no longer to make money, but to increase the amount of money they make. There's no stopping point, no "we're at a real good spot here". If some company managed to amass all the money in the world, it would be screwed because that would mean it can't make more money. Some companies may make some nice products and become profitable and have happy users, but even if a company makes enough money to give all of its employees a very comfortable life, it can't, because it needs to continue increasing its profits.

The greed is so apparent these days because too many companies have reached a point where there's no more room for them to grow, but they still need to.

And it'll only get worse.

There was a scene in the show Parks and Recreation that happens in some near future and that scene had an ad saying "Proud to be one of America's eight companies". That absolutely is the future we're walking towards.